Plt window title

Changed the window title from `"MonoGame Pipeline"` to instead show the `Application.ExecutablePath`.
This allows you to quickly identify which version of the pipeline tool you are looking at for people who regularly work with more than one version of monogame (eg, project1/monogame, project2/monogame). > Oops I just tried to build project1's content with project2's monogame...

The various pipeline.exe windows are otherwise/currently identical.